Answers

the results are correct.The apparently discrepancy you see results in how RapidMiner shows you the results.In the result view all numbers are rounded to four decimal places. If you copy and paste the coefficients in another editor you will see, that the actual results are:-0.0054453781512600165 and 9.999697478991262. And with these numbers you get:-0.0054453781512600165* 500 + 9.999697478991262 = 7.277008.

You can set the number of digits displayed under Settings -> Preferences -> General.